As for BZZ I imagine it will be two or three days, that's the usual turnaround. I'm interested to see which routes will be picking up the extra 789 capacity, I see a few of the NYC routes have been covered by them lately.
There's very little time between delivery and going into service now. G-VDIA only had a couple of days on the ground before she went into service.
Basically I think all VS (or any other airline) has to do is load the safety equipment and galley carts etc. (possibly the IFE system may need loading up with media too, not sure if or how VS does that?) and then off to work they go.
Also there's been a delay with the latest B789 deliveries so no doubt VS will want them in service as soon as possible.